Preheat oven to 350°F. Prepare your cupcake pan with liners.
Pour milk into a small bowl and add the lime/lemon juice. Whisk together with a fork and allow to set for 5 minutes. (This makes buttermilk.)
Sift together all dry ingredients (flour, baking powder, baking soda, and salt). Set aside.
In the bowl of a stand mixer fitted with a paddle attachment, beat the eggs for 30 seconds. Add the sugar and beat for another 30 seconds. Add the vanilla and oil and beat on medium speed for another 30 seconds.
Add 1/3 of the dry mixture to the bowl, pulsing the blade at first to avoid flour jumping out of the bowl. Mix until smooth. Scrape the bowl before adding the liquid. Add half of the buttermilk, beat, scrape.
Add half of the remaining flour, then the remaining liquid, and then the remaining flour. Be sure to scrape between each addition.
Scoop batter evenly into all liners, filling to 2/3 full.
Bake for 16-18 minutes, rotating half way through if your oven bakes unevenly.
Let cool in the pan for 1 minute, then carefully remove to a cooling rack.
This batter cannot be left to sit. It needs to be baked right away, so either half the recipe if you can only do one tray at a time, or use two trays and rotate their shelves in the oven midway through baking.